Recently, an image forming apparatus such as a scanner, a printer, a copy machine, or a multi-function peripheral (MFP) is designed to form an image of a document on an image sensor and read the image of the document using a light emitting element such as an LED and a lens array in which a plurality of lenses are aligned. In addition, an image of a light beam from the LED is formed on a photoconductive drum via the lens array using the light emitting element such as an LED and the lens array, and the image is formed (exposure) on the photoconductive drum. As the lens array, a combination of a plurality of lenses and apertures is exemplified. In addition, an imaging property and a variation in light intensity are significantly degraded in the lens array if optical axes deviate from each other between lenses through which one light beam passes.
There is also an imaging element array in which lens elements are integrally provided to avoid performance degradation and increase in cost due to a deviation during assembly. For example, the imaging element array is configured by a transparent part and an opaque part, and the transparent part includes two lens surfaces, namely an input surface and an output surface. In addition, the imaging element array includes a prism surface (reflective surface) for guiding light flux from the input surface to the output surface.
However, since the reflective surface is arranged at a position through which a wide light beam passes, high reflection accuracy is required over the entire wide region. Moreover, a long formation time should be set in order to enhance the accuracy. A deviation in a shape of the reflective surface from a designed value influences on disturbance of a wave front four times as much as the influence of a deviation in a shape of a transparent surface, and not desirable to arrange the reflective surface at a position of large light flux. In addition, two kinds of molded materials, namely a transparent member and a light shielding member and time and effort for setting an opaque part material in a transparent part material before molding are necessary, and there is a disadvantage in that molding of the imaging element array is not easily performed.